Hey all. . .been a while but I'm back. Summers coming and I've been working on my Cursed TA. So far I've had decent luck with it and it's at the point where the timing is dead on, car will fire up on the first crank and run great at an idle, and at cruising when pushing the pedal 1/4 of the way down it drives great and feels like it has tons of power. However, if I give it quick snaps, it bogs VERY bad, and if I hammer the gas, it will crap out and die, and ussually not start back up for a little while.

I have a holley 750cfm vacuum sec carb. It almost seems like the secondaries aren't opening at all. If I manually push the rod in, the engine revs up, but when messing with the throttle, they don't move whether quickly snapping it, or holding it down.

Any of these problems sound familiar to anyone?

 

Sounds familiar, but doesn't sound like a problem.

The secondaries are designed to open slowly so the fuel has a chance to make its way up the main circuit. The vacuum comes from the flow through the primaries, so unless you have the engine loaded, you aren't going to see the secondaries open by blipping the throttle in the driveway.

And, if you can feel the secondaries opening, that means they're opening too quickly. If you can't feel them open, you're pretty close to perfect.

 

im no carb guru by any means, but since nobody else has said anything yet, i thought maybe i would share my thoughts. id appreciate it of someone would correct me, but from what i know, vacuum secondaries are meant to open depending on engine load. so the engines only gonna use them if it needs them.

as far as the bogging goes, thats usually a sign of a lean situation. you should be looking for ways to provide more fuel. since your idle curcuit seems to be working good, i would stay clear of that. however i would be looking at things like the high speed circuit and accellerator pump. check to see that carb is giving the motor a good shot of gas what you crack the throttle open. this will compensate for that momentary lean situation.

also, im not sure about holleys, but i believe the quadrajets have 3 sets of jets. they have 2 idle jets, 2 power jets, and 2 midrange/tranfer jets. the latter of the three are supposed the be used for the transitions between the idle and high speed circuit. maybe the holley has something like this that can be adjusted?

hope that little bit of info helps somehow. best of luck!

edit: oops, looks like five7kid beat me to the punch

 

Thanks for the info. I will have to play with the accelerator pump and see if that helps at all. Where is it located on the carb. I am a FI guy, but I want to learn a little more about carbs. Also, anyone else have any help/input?? Thanks

 

The accelerator pump itself is on the bottom of the primary fuel bowl, driver's side. It's actuated via a couple of levers off the main throttle arm. There is an adjustment on the top of one of those levers. With the throttle at idle there should be no slack in the linkage- the accelerator pump should begin to move the instant the throttle arm moves. But don't get it too tight or you'll bottom out the pump when you get to WOT. You want it touching, under slight tension, but no more. Maybe half a turn more than the bare minimum needed to remove all slop from the linkage.

When you move the accelerator you should see 2 streams of gas squirting against the primary booster venturis when you look down the throat of the carb on the primary side. And they should start as soon as you begin to move the throttle arm. If no streams, or they look weak or bubbly, there are internal issues with the accelerator pump system and you'll need to open up the carb to fix them (i.e. it probably needs a basic rebuild).

 

Well I checked it out and fuel does shoot out of the two spouts at the top of the carb the second you touch the throttle, so I'm guessing thats not my problem, unless I need way more fuel than what it's actually shooting in. I have played with the timing, advancing it a little and retarding it a little and it doesn't help at all, and runs best right where it is supposed to be set (about 34 degrees advanced with vac advance disconnected at about 2700 RPM's).

Is there anything else that can cause an off-idle stall when stepping on it and flameballs to shoot out the carb?

 

i would go with a lean bog. which would mean you should adjust the power valve. accelerator pump cam and nozzel. if you read the tuning a holley on the top of the page it'll give you all the info you need to know to tune your carb.

so basicly whats happening.. your crusing along you smash on the air peddal car goes lean.. cause thats exactly what happened you added to much air for how much fuel is going into the carb. scince the carb it self without a accel pump and nozzel wouldn't be able to keep up with such a quick change in A/F. thats why the nozzel squirtz fuel into the ventruies. if thiers not enough for what you motor demands then you need to try a new nozzel head or accel pump cam.